The use of wire-guided catheter interventions for diagnosis and treatment of disease is increasing dramatically. Such interventions are employed in the arterial and venous vasculature, in the heart, kidneys, liver, and other organs, in the stomach, intestines, and urinary tract, in the trachea and lungs, in the uterus, ovaries and fallopian tubes, and elsewhere. As new miniaturized and less-invasive technologies are developed, the challenge becomes one of gaining access to the anatomical regions that could benefit from new forms of diagnosis and treatment. Wire-guided catheters provide a proven, minimally-invasive approach to reaching remote regions of the body and performing diagnostic and treatment procedures with precision, safety, and reliability.
A particularly well-known use of wire-guided catheters is for the treatment of coronary artery disease. In coronary artery disease, one or more coronary arteries becomes partially or fully occluded by the build-up of stenotic plaque, slowing or completely blocking blood flow to the heart muscle. If the heart muscle is deprived of blood, a myocardial infarction results, destroying heart muscle tissue and potentially leading to death.
Various coronary interventions have been developed to treat coronary artery disease. Angioplasty involves the use of a balloon catheter that is introduced into a peripheral artery and advanced over a guidewire to the target coronary artery. A balloon on the end of the catheter is expanded within the stenotic lesion to widen the coronary lumen and restore patency. It has been found, however, that in more than 30% of cases, restenosis occurs to again block the artery 6-12 months after angioplasty. To address this issue, coronary stents have been developed, tubular wire mesh scaffolds that are delivered via catheter to the coronary lesion and expanded into engagement with the wall of the artery to maintain its patency. While bare metal stents also experience a significant incidence of restenosis, the use of drug-coated stents in recent years has demonstrated a dramatic reduction in restenosis rates. Angioplasty and stents are also utilized in other vascular regions, including the femoral, iliac, carotid, and other peripheral arteries, as well as in the venous system.
Guidewires are commonly used to facilitate delivery of angioplasty and stent delivery catheters through the vasculature to the target lesion to be treated. Such guidewires are inserted through a vascular access site, usually a puncture, incision or other penetration in a peripheral artery such as a femoral or iliac artery. A guiding catheter is often used to cannulate the ostium of the left or right coronary artery, and the guidewire and other catheters are then introduced through the guiding catheter. Such guiding catheters typically include a hemostasis valve to facilitate insertion and withdrawal of devices while providing a hemostatic seal around the periphery of such devices to minimize blood loss.
The proximal end of the guidewire outside the body is threaded through a guidewire lumen in the delivery catheter to be used. If the catheter is an “over-the-wire” type, the guidewire lumen typically extends through the catheter shaft from the distal tip of the catheter to its proximal end. The disadvantage of such designs is that the guidewire must be very long in order to extend entirely through the catheter while the distal end of the guidewire remains positioned at the target lesion. Further, the process of exchanging catheters (withdrawing a first catheter from the guidewire and replacing it with a second catheter) is challenging and time-consuming with over-the-wire designs because in the region of the vascular penetration, the guidewire is covered by the catheter being withdrawn until the catheter has been completely removed from the patient, preventing the physician from keeping hold of the guidewire and requiring the use of an assistant to hold the proximal end of the guidewire some distance from the patient.
In response to these challenges with over-the-wire catheters, various types of “rapid exchange” catheters have been developed. In one design, the catheter has a shortened guidewire lumen that extends from the distal tip of the catheter to a point a short distance proximal to the balloon, stent, or other interventional element. This permits the use of a substantially shorter guidewire because the proximal end of the guidewire can emerge from the guidewire lumen a relatively short distance from the distal end of the catheter. This design facilitates faster and easier catheter exchanges because the shorter wire is easier to manage and keep sterile, and the shorter guidewire lumen allows the physician to maintain hold on the guidewire as the first catheter is withdrawn and a second is replaced. Examples are seen in U.S. Pat. Nos. 4,762,129, 5,980,484, 6,165,167, 5,496,346, 5,980,486, and 5,040,548.
In an alternative design, a guidewire lumen is provided through the catheter shaft from its distal end to the proximal end or to a point a substantial distance from the distal end, as in over-the-wire designs. However, the catheter wall has a longitudinal slit in communication with the guidewire lumen over all or a portion of its length. This allows the proximal end of the guidewire to exit the guidewire lumen through the slit at any of various locations along the length of the catheter. In some designs, the guidewire is threaded through a zipper-like device that slides along the longitudinal slit to insert or remove the guidewire from the guidewire lumen. Examples are seen in U.S. Pat. Nos. 6,527,789, 5,334,187, 6,692,465, Re 36,587, and U.S. Pat. No. 4,988,356.
While rapid exchange catheters have many advantages over over-the-wire designs, current rapid exchange catheters suffer from certain drawbacks. For example, in those rapid exchange designs having a shortened guidewire lumen, the guidewire is exposed outside of the catheter and runs alongside the catheter for a substantial distance within the vessel from the vascular access site to the point at which the guidewire enters the guidewire lumen. In “zipper” type designs, while the guidewire may be enclosed within the catheter in the vessel, the guidewire lumen is integral to the catheter shaft between the distal and proximal ends thereof, increasing its profile and stiffness.
For these and other reasons, improved interventional devices with rapid exchange capabilities are desired. The interventional devices should provide the benefits of conventional rapid exchange catheters, including allowing the use of shorter guidewires and facilitating catheter exchanges by allowing the physician to continually hold and manipulate the guidewire from a position near the vascular access site as a catheter is withdrawn and replaced. Further, the interventional devices should keep the guidewire fully enclosed in the guidewire lumen within the vessel between the vascular access site and the catheter balloon, stent, or other interventional element on the catheter. Additionally, the interventional devices should have a shaft of minimal profile and stiffness in its proximal extremity.